Telephone system having code call facilities



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Dec. 20, 1949 Q. A. PEARCE TELEPHONE SYSTEM HAVING CODE CALI: FACIIJTIES Filed July 27, 1945 12 Sh'eet heet l INVE OR OWEN Avis CE ATTO Y Dec. 20, 1949 o. A. PEARCE TELEPHONE SYSTEM HAVING CODE GALL FACILITIES Filed July 27, 1945 v 12 Sheets-Sheet 2 INVE NTOR OWEN AVIS PEARCE Y E N R O w A Dec. 20, 1949 o. A. PEARCE.

TELEPHONE SYSTEM-HAVING CODE CALL FACILITIES 12 sheets-sheet 3 Filed July 2'7, 1945 LORZ |NVENTOR OWEN AVIS PEARCIE Pal XVR4

Dec. 20, 1949 o. A. PEARCE TELEPHONE SYSTEM HAVING CODE CALL FACILITIES Filed July 2'7, 1945 l2 Sheets-Sheet 4% PTY was

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INVENTOR OWEN AVIS PEARCE Dec. 20, 1949 o. A. PEARCE v 2,491,90

TELEPHONE SYSTEM HAVING CODE CALL FACILITIES Filed July 27, 1945 12 Sheets-Sheet 5 TA2 551 W W INVENTOR OWEN AVIS PEARCE ATTORN EY Dec. 20,1949 0. A. PEARCE it" L903 TELEPHONE SYSTEM HAVING CODE CALL FACILITIES Filed July 27, 1:.945 l2 Sheets-Sheet 6 f g 'og a.) o fl F e04 K2 LFM OVER FDR swe LINKS PTY A53 A51 A55 A54 A56 A52 INVENTOR OWEN AVIS PEARCE ATTORNEY Dec. 20, 1949 l I o. A. PEARCE 2,491,903

TELEPHONE SYSTEM HAVING CODE CALL FACILITIES Filed July 27, 1945 12 Sheets-Sheet '7 CR5 NR3 RMC D2 E4 .-N1 I N3 100 YA 2000 YE D4 LL1 LP l4! L0J v 22 43- 44 CR4$\ RA 45 QT *RB1 INVENTOR OWEN AVIS PEARCE ATTORNEY Dec. 20, 1949 o. A. PEARCE 2,491,903

TELEPHONE SYSTEM HAVING CODE CALL FACILITIES Filed July 27. 1945 12 Sheets-Sheet 8 F6 H5 CR7 K6 D6 03 H l in zco FSM T I 2 l M E k CCM ccs CCL INVENTOR GWEN AVIS PEARCE ATTOR N E Y o.-A. PEARCE 2,491,903

TELEPHONE SYSTEM HAVING CODE CALL FACILITIES Filed July 27; 1945 Dec. 20, 1949 12 Shets-Sheet 9 sun 6UF5 f 51 so 6OF1 N 6OF5 6K2 GOFZ A\ sons 6K5 LFM 6K [5:] 4+4- T A\ ecos A W 6001 GM H soFMc euFMc unms DM FDR OVER sws A56 A53 A55 A51 A54 INVE NTOR. OWEN AVIS PEARCE ATTORNEQ Dec. 20, 1949 o. A. PEARCE 21,491,903

TELEPHONE SYSTEM HAVING CODE CALL FACILITIES Filed July 27, 1945 12 Sheets-Sheet 10 6P1 if:

INVENTOR 0 WE N AVIS PEARCE ATTORN EY U. A. PEARCE TELEPHONE SYSTEM HAVING CODE CALL FACILITIES Dec. 20, 1949 12 Sheets-Sheet 11 Filed July 2'7. 1945 LL1 LL12 OWEN AVES PEAR'G E ATTORNEY Dec. 20 19419 0. A. PEARCE 2,491,903

TELEPHONE YSTEM HAVING CODE CALL FACILITIES Filed July 2'7, 1945 l2 Sheets-Sheet 112 I 15 121 15 4 j 0 1s 122 16 14 17 123 17 24 18 131 18 34 19 132 19 41 INVENTOR OWEN AVIS PEARCE ATTORNEY Patented Dec. 1949 UNITED STATES 9 F FICE Application .Tuly 27, 1945.,Seri'allN'o. 607,473 In Great Britain August I944 7'Glaims. (crime-1's The present invention relates to telephone systems andis more particularly concerned with privates'ystems providedwith so i called codecalling facilitiesi; e; arrangements forgiving audible and/or visualcode signals at various points-div posed over the premises served by the system to indicate that someone-is endeavouring to make contact witha particular party who has left the telephone reached bymaking use of his regular telephone number;

In'previous systems of this typea par-tycalling and receiving no reply has needed to hang up and dial a special number characteristic of the wanted party in order to initiatethe code-call ing'operation; This involves additional timeand trouble-and the chief object of the invention isto simplify and improve the procedurewhich'has hitherto been considered necessary forgiving facilities of the kind in question;

According to one feature of the invention in a. telephone system including facilities for code calling, arrangements are provided to enable-1 a calling party'who is unable to contact a wanted partyover the telephone toinitiate-the'appro priatecodecall by the performance of a distlnctive operation at the callingtelephone withoutreleasing theconnection initiallyset' up; the dis tinctive: operation being the same regardless i of the wanted-party.

According to another feature of the invention: 1

in a: telephone system includin arrangements for the code calling of: parties=whotare absent:-

with Figs. 1-8 and 16-19 of the coependingap plication of Owen A..Pearce eta; al.-,.Seria1 No'. 607,472, filed July 2.7, 1945, which: gives a full? descriptionof certainespectsot the system disclosed which arenotclosely relevantrto the present invention.

Fig. 1 shows the; essential trunkin arrange ments ofthe boa-rd,

Figs. 2-5 when arranged in themannerindi cated in; Fig. 2 show. circuits of two subscribers line equipments and of the local and special service' link finderallotting equipment and ass ociated' start relays; In Pier 3' an explanatory inset is. included to simplify the understanding of the finding operations involved on origination of a local call.

Figs; 6; 7 and 8' when arranged side by side with-Fig: Gonthe left showthe circuit ofa local finder/connector link, hereafterreferred' to as a the under'5'0andover groups into which lotting' equipments; such as the one designated AE, are provided forany'size' ofboard'up to lines, each" one normally serving its own group. of-'5'0-lines butcapable; under fault conditionsof" serving the other "group also:

When a'calling'subscriber such as snrimtietes.

a call, the line equipment LE extends a start signal to the" appropriate allotting equipment such as -AE tocause a local linksuch as LL; to asg sociate-itself with the calling line, the required oheofthetwo finder switches shown being. determined: in accordance with the particular 50 line-group in'which the calling party is located. Thesetting'uppf local calls is performed in orthodox: manner b ydialing' on to the local link con lIGCtOI" switch:

As regards the setting up of certain special? servicecallswhich' is'eiiected either by dialing a} special code" number or: by dialing a normal P." A: X'telephone number followedb'y, a suitable extra digit; thefinder "switches of both lobafand" special service links are adapted" to be allotted by eachcommon a-llotting equipment; discrimination as to the allotting function to be performed by this equipment" being efieotedby pro;

violing separate discriminating relay for eaclii service" concerned: Consequently; as will be ap preciated from theensuing description; on'rieceipt off the appropriate digit or digits the allot-ting equipment causesthe special service link" concernedtoassociate itself witlrthe calling line'on a finder basis, whereupon the local link previously employed is released for further common use. Typical special service links which operate on this principle and are shown in Fig. 1 include the tie line service link TLL and an unspecified special service link SSL which might be a fire alarm service link or a watchmans service link.

Considering now the operation of the various circuits of Figs. 2-12, in those circuits, which are assumed to be operated off a 50 volts supply, typical resistance values of certain relay windings and resistors are shown for general guidance. The mechanism of the connector switch in each local link is of the type disclosed in the patents to Robert N. Saxby No. 2,028,689, granted January 21, 1936, and No. 2,124,750, granted July 26, 1938.

Referring now to Figs. 2-5, Fig. 2 shows the line circuits of under 50 and over 50 subscribers, the lines of which are respectively designated SLU and SLO. In the upper part of Figs. 4 and 5 is shown the under 50 allotting equipment UAE, while in the bottom part is shown the set of leads extending into the over 50 allotting equipment OAE. In the centre is shown the control and timing relay set ACTS including the switch TS which serves both of the allotting equipments UAE and GAE. Each allotting equipment is provided with an 8-level uniselector such as AS, the banks of the uniselectors in the two allotting equipments being multiplied together and sets of leads such as Over, PTY, Links, extending therefrom to the local and the various special service links. The twelve local links with which the board, when at full capacity, will be provided, are designated LLlLLl2, the eight tie line service links are designated TLLiTLL8, while the fire alarm, code call and watchmans service links are designated FAL, CCL and. WL respectively. A set of leads also extends from the multiplied allotting switches to the common access portion of the circuits of the various conference equipments CE which are provided on the board.

, Fig. 3 shows the set of service discriminating relays which serve both of the allotting equipments UAE and OAE, a separate relay being provided for the local links and for each special service with which the board is provided.

, Considering now the setting up of a local call from a non-priority subscriber in the under 50 group, for this purpose reference should be had to Figs. 2-5 and to the local link circuits of Figs. 6-8.

When the subscribers line such as SLU, Fig. 2, is looped, relay LU operates and since the subscriber is assumed not to have priority facilities, relay LU in operating will complete a circuit to operate the allotting equipment UAE start relay ST, Fig. 4., and the service discriminating relay LOC, Fig. 3, in series as follows: earth, Winding of relay ST, common lead l2, resistor LYB, Fig. 2, contacts LUl chain-dotted cross-connection to common lead ii, resistor LYA, lead 16, contacts LOR3, Fig, 3, winding of relay LOC, common lead 22 and resistors YE and YA, Fig. 7, in each local link and contacts Ni, RMC, Cl, E2, B4 and CR3 to battery via the connector switch rotary magnet RM (non-operative in this condition) Relay ST at contacts ST! brings up relay SS, which at contacts SS2, Fig. 5, connects relay LK up to the allotter switch Links test wiper ASS and at contacts SS3 completes a self-interrupted driving circuit for the allotter switch magnet ASM via its interrupter contacts ASMC.

Relay LOC, Fig. 3, at contacts LOCI, Fig. 5, connects earth to contacts 2-l3 of bank AS8 so that earth will be applied via wiper AS8 to relay LK while the switch AS advances its wipers over contacts extending to the twelve local links LLl-LL!2. At the same time contacts LOCI ensure that other link circuits having less priority as regards finding than the local links are unable to exert any control over the allotter at this time. It will be noted, however, that the fire alarm link, the service discriminating relay for which is designated FA, can always take priority, since the earth to the other relay contacts is communicated via contacts FAi.

Switch AS proceeds to rotate its wipers over the twelve local links, and when a free one is found such as LLB disclosed in Figs. 6-8, relay LK operates quickly in series with the idle marking battery which is connected up to allotter bank AS6 over the following circuit: battery, magnet RM, Fig. 7, contacts CR3, B l, E2, Cl, RMC and NI, resistor YA and the Links lead which extends to contact :2 on bank Owing to the low resistance (11 ohms) of relay LK, this provides an immediate guard on the outlet seized. This relay in operating, at contacts LKi completes a local locking circuit, and at contacts LK2 disables the magnet ASM driving circuit by introducing high resistance relay VR in circuit therewith.

Relay VR in operating in series with magnet ASM, at contacts VH3, Fig. 4, applies earth via contacts FTi and wiper and bank AS3 to the DM lead so as to complete a self-interrupted driving circuit for the magnet UFM, Fig. 6, of the under 50 finder switch UF in the selected local link. At contacts VR i, Fig. 5, relay VR extends earth via the low resistance windings of relays FT and PR in series and wiper and bank ASS on to the FDR lead which connects with the local linkfinder switch wiper UF l, Fig. 6. Contacts VR5 bring up relay LOR, Fig. l, which at contacts LOR2 LOR8, Fig. 3, opens the circuits of all the service discriminating relays, Contacts VRB, Fig. 5, look relay VR, while contacts VRT apply a 200- ohm marking battery via resistance AYC and wiper and bank AS? to the start lead [6, Fig. 3, over which it extends via the 250-ohm resistance LYA, Fig. 2, common lead H and contacts LUi to the M lead of the calling line circuit which is connected to a particular set of contacts in the bank multiple LFM of the various local link under 50 finderswitches. This marking battery potential furthermore holds relay ST via resistor LYB and common lead l2.

The selected local link finder UF proceeds to rotate its wipers and when wiper UF4 encounters the 450-ohm marking battery via resistors LYA, Fig. 1, and AYC, Fig. 5, relay FT, Fig. 4, will operate but relay PR, Fig. 5, will fail to operate owing to the resistance of the circuit. Relay FT at contacts FTi opens the earth supply to the DM lead so as to halt the movement of the finder switch UF and also extends earth via its left-hand winding and wiper and bank AS4 and lead SWG to hold itself in series with relay A, Fig. 6, in the local link which operates, while contacts FTZ short-circuit and relay SS. The 12-ohm resistance of relays FT and PR applied to lead FDR and extending back via wiper and bank UF4, Fig. 6, and the M lead to the calling line circuit short-circuits and releases relay ST, Fig. 4, which was initially operated over lead i2 and resistance LYB, Fig. 2. Relay SS on releasing at contacts SS2, Fig. 5, opens the circuit of relay LK which releases, whereupon contacts LK2 short-circuit relay VR. Relay VR commences to release slowly and during this time magnet ASM is energised. The various operations involved will be better appreciated from the inset diagram in Fig. 3 which shows only the elements immediately concerned.

During this time relay vA, Fig. 6, in operating will .havebrought up relay B and this relay at contacts BI prepares a circuit for relay C, at contacts B2 applies earth via relay K to wiper UF3, at contacts B3, Fig. 7, prepares an impulsing circuit for the connector switch vertical magnet VM, at contacts B4 disconnects the incoming idle marking battery circuit via magnet RM, and at contacts B lights the supervisory lamp LP via battery-connected delayed alarm equipment connected to common lead 45.

Relay K on being connected to wiper UF3 now operates over the P lead in series with relay KU, Fig. 2 of the calling line circuit. Contacts KI and K2 complete a holding circuit for relay A via the calling subscribers loop, while contacts K5 complete a balanced dial tone circuit from the earthed dial tone source connected to common lead DTE. Relay KU, Fig. 2, at KUi releases relay LU and at KU2 removes earth from the positive lead. Contacts LUI thereupon open a point in the operating circuit of relay FT, Fig. l, which, as previously mentioned, had been initially completed via lead FDR, finder wiper UF l and the M lead, but this relay remains held over the SWG lead in series with the local link A relay. When relay VR releases, contacts VR3 open the holding circuit of relay FT in series with relay A, the latter now continuing to hold over the calling partys loop. At contacts VR4 a further point in the operating circuit of relay FT is opened, at contacts VRB magnet ASM is tieenergised to step on the AS switch wipers to the next position, and at contacts VRl the marking battery circuit via resistor AYC is opened.

.All relays in the allotting equipment UAE are now normal, and this equipment is therefore ready for further common use. Relay KU in the local line circuit and relays A, B and K in the local link remain held.

The calling subscriber now dials the required number and assuming a local subscriber is required, a two-digit number will be dialed.

When the first digit is dialed, relay A in responding repeats the impulses to the vertical magnet VM, Fig. '7, at contacts A2, the switch wipers being thereupon raised to the corresponding level. Relay C operates on the first relase of relay A-and relays B and C then hold by periodic short-circuiting during the train. On the first vertical step, the switch off-normal spring set N is mechanically operated and at contacts NI, Fig. l

7 prepares the release alarm circuit over common lead 43, at contacts N2 prepares a circuit for relay E and at contacts N3 disconnects the circuit for lamp LP.

At the end of the train of impulses relay B holds and relay C releases slowly. On the release of relay C, relay E operates in series with magnet VM (non-operative in this circuit) and at contacts EI disconnects the dial tone circuit, at contacts E2 further prepares the release alarm circuit via common lead 44, at contacts E3 prepares the impulsing circuit to the switch rotary magnet RM, and at contacts E5, Fig. 8, prepares a circuit for relay H.

The second digit dialed is effective on magnet RM, whereupon the switch wipers are rotated over the selected level, relays B, C and E holding operated during the train. On the first rotary step the rotary off-normal springset NR is mechanically operated and at contacts NRI;

.Fig; 6, i'urther disconnects the :dial tone circuit and prepares a circuit for the application of busy or ringing tone over common leads BTE or RTE respectively, at contacts NR2 disconnects the vertical magnet circuit and at contacts NR3 further prepares a circuit .for relay H and disconnects any re-operating circuit for relay At the end of the train, relay B again holds and relay C releases slowly. On the release or relay C, relay E commences to release slowly and relay H thereupon tests the called line 5? lead. Assuming the line is free, relay H operates in series with the subscribers cut-oil relay "and at contacts HI short-circuits its 1800 ohm winding to provide a low resistance guarding potential and also to enable the cut-ofi relay to operate and so to disconnect the line relay from the line. At contacts H2, Fig. 6, ringing tone is returned to the calling party via common lead RTE, at contacts H3 a locking circuit is prepared for the ring trip relay F, While at contacts H4 and H5 ringing is applied via common lead ll and the upper winding of relay F to the called line, the return circuit being completed via the battery connected common lead 42. At contacts H6 a circuit is prepared to the code call equipment and at contacts H'I the M lead is extended through from the called to the calling side of the circuit for the purpose of selective nnding as will be described later.

When the called subscriber replies, relay F operates suificiently to open its break-first con tacts FI, whereupon the lcwer winding comes into action to cause it to operate fully and in so doing at contacts F2, Fig. 6, it cuts off the ringing tone circuit and at contacts F3F6, Figs. 7 and 8, it connects battery feed to the called party via the windings of relay D which operates. Contacts of relay D are without effect as far as the present circuit operations are concerned.

At the end of conversation if the called sub-' scriber hangs up first, relay D releases and at contacts D4 lights the supervisory lamp LP via the delayed alarm equipment connected to common lead 45.

When the calling party hangs up, relay A releases whereupon relay B commences to release slowly and relay C re-o'perates. On the release of relay B relay E re-operates and relay K, Fig. 6, and relay KU, Fig. 2, release whereupon relays F and H also release. Relay RB, Fig. 7, operates on the operation of refay E and shortcircuits the 1000-ohm winding of relay RA. On the release of relays C and E in turn a selfinterrupted driving circuit is completed for the rotary magnet RM via the 4-ohm winding of relay RA and earthed contacts RBI. Accordingly the wipers are rotated clear of the banks, after which they fall and rotate under the banks by spring tension back to their normal position where the off-normal contacts NI open and disconnect the release circuit. During this time relay RB remains held due to its slug. If the switch fails to release, on the release of relay RB relay RA holds operated over its two windings in series with the rotary magnet RM, and at contacts RAI completes a circuit to alarm equipment connected to lead 46.

If the calling party hangs up first relays A, B, K, KU and 0 release in turn and relay E. is operated and at contacts E4 lights the super= visory lamp LP. When the called party subsequently hangs up, relays D, H, F and E release in turn and the switch is restored to normal under the control of relays RA and RB as just described.

Assuming now that the called subscriber is found to be busy, relay H will fail to operate during the slow release time of relay E and a circuit will then be completed via contacts El, Fig. 6, to return busy tone to the calling party from the busy tone source connected to common lead BTE. When the called party hangs up, the switch restores to normal as described, the only difference being that in this instance relays F and H will be already normal when relay B releases.

It will now be assumed that the calling party has priority facilities in which case relay LU in operating will atcontacts LU! connect the M lead direct to lead it via the dotted connection and common lead Ill instead of via resistance LYA as in the case of a non-priority subscriber. Hence when the local link finder UF connects with the calling line, both the series testing relays FT and PR in the allotting equipment UAE will operate. Relay FT functions as already described, while relay PR at contacts PRI (Fig. 4) extends battery via resistor AYA, contacts VRZ and wiper and bank ASZ and the PTY lead to energise the local link relay D, Fig. 7 which at contacts Dl locks over its upper winding via contacts B3 and H3 to earth.

In response to the dialing of the two local digits the circuit again functions as described and if the line is free, relay H at contacts H3 disconnects the locking circuit of relay D which subsequently re-operates over the called subscribers loop in the usual manner after the operation of relay F.

If the line is busy however, the calling party on receiving busy tone, since he has priority facilities may effect connection with the busy wanted party by dialing a further digit such as 0. At this time relays A, B, K and D will be operated and in response to further dialing relay C will r operate and complete a charging circuit for capacitor QA, Fig. 8, during the train via resistor YF, contacts E5, NR3 and B5 to earth.

At the end of the train relay C at contacts C l connects the charged capacitor QA across relay: CR. If the further digit has been of sufficient duration, the charge accumulated on capacitor QA will energise relay CR sufficiently to close its make-first contacts CRI, after which it fully operates via these contacts and contacts D8 and H l to earth. Relay CR also at contacts CR3 disconnects magnet RM, and at contacts CR5 reoperates relay E, whereupon at contact El the tone circuits are disconnected. At co 1 acts CR6 and CR7 the speaking'leads are connected via contacts D5 and D6 through the parties already in conversation. If the incoming call is urgent, the parties in conversation should now hang up, whereupon since relay E will have prepared a circuit for relay H at contacts E6, this relay'will now operate in series with the called partys cutoff relay. Relay H atcontacts I-I! disconnects relay CR, whereupon owing to the opening of contacts CR5 relay E commences to release slowly. On the release of relay E contacts Fig. 8, complete a circuit for ringing the called party. When the called party answers, relay F trips the ringing in the usual manner, and relay D then operates over the called loop.

In connection with the measurement of the extra digit, instead of measuring a minimum duration, by means of relay C, counting arrangements might be employed in the local link wherebefore priority cut-in can be efiectecl. The use of an extra digit to provide a control feature for a calling party avoids the need of push buttons or the like which would otherwise be required on or in association with subscribers telephone instruments. It will be appreciated that manual control of the priority cut-in feature has the effect of preventing a lower ranking executive from automatically cutting in on a busy higher ranking executive.

It will have been noticed that the priority marking is extended to the local link via the allotter circuit at the time of finder switching. This obviates the need for special signaling arrangements from the calling line circuit through to the local link line finder.

Dealing now with a call originated by a sub scriber in the over 50 group, when line SLO, Fig. 2, of such a subscriber is looped, relay LO operates and functions in similar manner to relay LU except that instead of relay ST, Fig. 4, in allotting equipment UAE being brought up in series with relay LOO, Fig. 3, an equivalent relay in the over 50 allotting equipment OAE will be operated over common lead N), Fig. 2, in series with rela LOC.

When the allotter switch associated with equipment OAE finds a free local link and relay VR operates, contacts VRI come into operation in this instance to extend earth from contacts TRI, Fig. 4, in the timing set ACTS on to allotter wiper ASl via which the earth extends to the Over lead extending to the local link. If the link of Figs. 68 has been taken into use, relay CO, Fig. 6, will be operated over this lead and will bring the over 50 finder switch OF into operation instead of UF. Thereafter the call proceeds as for the under 50 case already described.

A full description of the arrangements for automatic changeover of the allotting equipments if abnormal conditions arise is given in the co-pending application previously mentioned but is not included herein as it is not necessary for a proper understanding of the present invention.

Consideration will now be given to the setting up of a code call connection to a wanted subscriber who is absent from his telephone location. For this purpose the line of a wanted party is connected with in normal manner via a local link and if there is no reply, or if the reply is made by a third party who is then requested to hang up, the caller will dial a further digit such as 0 as a result of which a start signal is extended to a code call link and the wanted line concerned is marked in the banks of a finder switch in this link. This finder switch then searches for and switches to the marking, the position of the finder switch being thus characteristic of the wanted line concerned and so determining the appro-,

priate code which is then sent out in visual and/ or audible form to suitable locations about the premises. On the positioning of the code finder switch on to the wanted line, a second finder from any telephone whereupon connection be-.

tween the two parties is completed by way of the code call link, and the code calling signal is disconnected. At the end of conversation the code call link is only released when both parties hang up. Should a caller attempt to originate a code call to a subscriber not having this facility, or if" the code call link is engaged when a code call is originated, busy tone isreturned to the caller.

It is. not essential that the code call link on being started up. should associate itself with both the called call ng lines. since onlarge P. A. X boards Where many local links are available for use the code call link could simply connect up with a local link, both the local and code call links being utilised in series during the transmission of the code calling signal and the subsequent conversation.

Referrin now to the details o the circuit of the code call link COL shown in Fi s. 9-12, when a calling party, after having dialed the line of a. party having code call facilities on to a local link such as that shown in. Figs. 6-8, finds there is no reply or if the re ly is made b a third party who is then req ested to hang up, the caller will dial an extra di it such as which is effective as previously described to bring up relay CR. Fig. 8, in the local link in addition to relays A, B, K and H which are operated ii there has been no. reply or relays A, B, K, F and H which are operated if the party replying has again hung up., Relay CR in operating, at contacts CRI connects itself on to common lead CCS extending to. the code call link, whereupon relay ST, Fig. 11 is operated, in series with relay CR which holds. Relay CR also at contacts CR4 marks the wanted line. concerned on the banks of the socalled code finder switch SFA or EFB, Fig. .11, the two. Switches together giving access to a maximum of 47 lines with code call facilities as will be seen later. The line marking is eiiiected by means of battery potential via the upper Winding of relay SSH, Fig. 11, in parallel with resistor BYF which extends over common lead COM to Fig. 8 and then via contacts CR4 and H! in the local link and connector switch M wiper which is positioned on the called line M lead, which lead, since it is associated with a line having code call facilities. will connect up with a position in the M bank 6FA3 or GFB3 of the code finder switch 6FA or BFB.

Relay 6ST in operating at contacts 6ST! brings up relay GSR over its lower Winding from an earth via banks and wipers GFBB and 5FA5 and contacts BKBTI and EKKZ, 6KR3 and 5P4. Relay SSR in operating, at contacts 6SR2, Fig. 10, prepares for tripping ringing from the local link via. resistor BYC in case the call to the wanted line had not been answered. at contacts 6SR3, Fig. 11, connects up rela EKK to the seriesconnected wipers FAB and tFBG, and at contacts, 6SR5 completes a driving circuit for the BBB switch magnet BFBM via magnet interrupter contacts GFBMC, whereupon switch GFB commences to rotate its Wipers from the home position. 0 in search of the particular Wanted line concerned, which as previously described is marked by battery potential via the winding of relay 65R in parallel with resistor dYF.

Assuming now that the marking does not appear in the SP3 switch banks but instead in the BFA switch banks, switch (BFB will rotate through to position 24 which is unwired except for the M bank so that relay GKK will then rapidly opcrate from a local marking battery comprising the winding of relay BRS and resistor FYE in parallel. Under this condition relay SKK in operating simply opens the magnet driving circuit at contacts BKKZ, Fig. 10, while rela EiRS at contacts SRSI completes a locking circuit for itself via. contacts BSRA, relay tSR after having been held' during; the hunting operation over its 10 lower winding now remaining held for a further short interval due to its slug. Contacts GRSI also short-circuit relay GKK while contacts 6RSZ prepare a self-driving circuit for magnet EFAM of switch 6FA so that when relay BKK releases, contacts GKKZ will complete the driving circuit for magnet fiFAM. When switch BFA steps to the first effective position 1, the driving circuit is maintained independently of wiper and bank BFBE and the wipers continue to rotate until the marked wanted line is encountered. When, this occurs, relay BKK now operates rapidly from the marking battery on the M lead in the connector switch multiple FSM and opens the magnet driving circuit at contacts tKKZ while at contacts iiKKi battery via the high resist ance relay GKR is connected over the P wiper and bank BFA lto the P lead of the marked want-. ed line on which lead the called subscribers cutoff rela is holding operated in series with the low resistance guarding winding of the H relay in the local link. Relay EKR operates under this condition without disturbing the relations beween, relay K and the calling subscribers cutoil relay and thereupon at contacts EKRE, Fig. 10, prepares for the starting up of the calling line finder tUF or F in the code call link, at contacts GKRZ completes a holding circuit for itself, at contacts 6KR3 completes an operating circuit for relay 6K3, and at contacts sKR l and tKRfi, Fig. 11, connects resistor 6Y0 across the negative and positive conductors, so. that if ringing current is being sent out from the local link, the F relay therein is tripped and on operation of this relay the called subscribers battery feed-. ing relay D, Fig. '7, is energised. If the ringing has already been tripped in the local link due to the call having been answered relay D is operated immediately relay B-KR operates. Relay BKB at contacts BKBI completes a locking circuit for itself independently of relay GSR, :at contacts 6KB3 connects up ringing return battery via common lead 9!] and resistor iiYB to the negative contact of the answering code number in the connector switchmultiple FSM, at contacts 6KB5 connects relay HP to the appropriate P con tact, at contacts BKBG, Fig. 11, connects busy tone from common lead BTE on to common lead CCB so that bus tone would be returned to the calling subscriber via the windings of relay A, Fig. 6 but for the fact that relay CR, Fig. 8, is released on the operation of relay D, Fig. 7, and at contacts. BKB'I completes an operating circuit for relay 6S0 viathe particular code finder switch magnet concerned (non-operative in this condition). prepares a locking circuit for itself and at contacts 6802, Fig. 11, brings up the pulsing relay 6PU.

Returning to the release of relay CE in the local link on the operation of relay D, it will be remembered that this relay was held operated in series with. relay EST and this latter relay will therefore alsohave released provided no other code calling is in prospect. If a second local link requires the code call link at this time, relay 6571 will remain operated and the CR relay in the second local link in operating in series with the relay 6ST will complete a circuit to return busy tone to the second calling party via common lead CCB anclcontacts CR2, NIH and El, and the windings of relay A such as in Fig. 6. Relay GR in releasing in the local link concerned in the present description, at contacts CR2 prevents busy tone on lead CCB from being re Relay 680 in operating at contacts tSCl.

turned to the calling party and at contacts CR4 disconnects the M lead circuit over which relays BKK and BSR are being held in series. Relays BKK and tSR now release, whereupon at contacts ESRZ the resistance termination of the negative and positive lines via resistor GYC is replaced by relay BA, whereupon relay D, Fig. '7, releases, while at contacts SSRA, Fig. 11, the circult of relay 6R8 is opened. The release of relay 6R8 is without effect at this time.

On the release of relay BSR a circuit is also completed to start up a calling line finder switch in the code call link in the following manner. From reference to Fig. 3 it will be seen that battery via the code call link service discriminating relay SC normally extends over contacts LORE and lead 25 into Fig. 10 whence it extends through to contacts EKRI. When relay ESR releases this battery will be extended over contacts 6SR3 and then via wiper and bank GFAS or wipers and banks 6FA3 and eFBS as the case may be, to the M lead extending back to the calling local link and thence over the connector switch M bank and wiper, and contacts I-I'l, CR4, K3 and CO6 to the local link finder switch wiper and bank UFA (assuming the calling party to be in the under 50 group) which connects over the finder switch multiple LF with the M lead of the calling line circuit, Fig. 2, where a circuit will be found via resistor LYB and common lead l2 to earth via relay ST, Fig. 4, in the allotting equipment UAE. Both relays SC and ST operate over this circuit, relay SC at its contacts SCI, Fig. 5, determining the finding priority of the call in question and relay ST functioning in usual manner to initiate the stepping of the allotting switch AS. When this switch reaches position 23 extending to the code call link CCL, an earth is connected up to relay LK, Fig. 5,

via bank and wiper A88 and this relay thereupon switches in over the Links lead to the idle marking battery of the code call link via resistance BYA, Fig. 9. Relay VR then operates and in usual manner brings up relay LOR, Fig. 4, while relay FT is connected up to the FDR lead. At the same time earth is extended over the DM lead to cause the under 50 line finder switch BUF in link CCL to search for the calling line.

When the calling line is found, relay FT operates over the FDR lead and wiper and bank SUFQ and the circuit previously traced except that the battery connection to lead 25 by way of relay SC is now replaced by battery via resistor AYC, contacts VR'! and wiper AS'l in 23rd position. Relay FT in operating disconnects the finder switch 6UF driving circuit over the DM lead at contacts F'Tl, Fig. 4, and at the same time extends earth via its left-hand winding and the SWG lead to bring up relay 5K, Fig. 9. The allotting equipment proceeds to release in usual manner and relay 6K in operating looks over contacts SKI, at contacts 6K2 and 6K3 extends the calling loop through to relay 6A which operates, at contacts 6K4 applies earth to the P wiper 6UF3 to force down the series holding K relay in the local link and hold the calling partys cut-off relay, and at contacts 6K5 opens the circuit of relay GKR in the absence of the alternative dotted connection the purpose of which will be described later. Relay SKR thereupon releases and at contacts tKRI opens the circuit of start lead 25, and at contacts 6KR3 renders the continued holding of relay BKB dependent on relay 6A. In the local link relay K in releasing, at contacts KI and K2 opens the circuit of relay A which thereupon'releases and in the iii previously described manner initiates the release of the local link for further use.

Returning now to the operation of rela .BKB which occurred when the code finder found the wanted line, it will be remembered that this relay brought up relay BSC Which at its contacts 'oSCZ brought up relay BPU, Fig. 11. Relay BPU in operating at contacts 6PU2 completes an energising circuit for the switch magnet SSSM, Fig. 11, whereupon the magnet interrupter contacts SSSMC disconnect the circuit of relay BPU. Magnet BSSM and relay GPU interact to cause theswitch SSS to advance step-by-step over its banks, whereupon in dependence on the positions of the wipers of code finder switch BFA or SFB a suitable code will be sent out in visual and/or audible form to suitable locations about the premises. At the same time contacts EPUI, Fig. 10 extend tone pulses from common lead 9| back to the calling party.

The sending out of the code calling signals may be done in any known manner for instance by dot and dash audible codes or by spelling out the number on lamps. By way of example it is assumed as shown in Fig. 12 that the calling signals are set up on lamps for which purpose four lamps designated 1, 2, 3 and 4 and an alarm bell 92 which connect up with the code call link over leads 9391 are provided at each suitable loca tion about the premises, the lamps and bells either being directly operated as shown or indirectly operated in local circuits by means of directly operated responding relays. The function of the alarm bell is to give a warning just prior to the commencement of each lamp signaling cycle.

Referring now to Fig. 12 and assuming for example that the wanted line is marked on the home position 0 of the code finder switch BFB in which instance relay 6KK will have operated with th wipers in the home position shown, during the interaction of relay BPU and the switch magnet SSSM, wiper GSSZ in rotating over the bank arc will cause lamp No. 1 to flash once during each of three spaced signaling periods. If switch 6FB is positioned on position 1, lamp No. 2 will flash once during each of these periods. If switch 6FB occupies position 3 lamp No. 1 will be flashed twice in succession during each of these periods, while if switch GFB occupies position 4 lamps Nos. 1 and 2 will be flashed in succession during each of these periods. If the switch SFB is in position 12, lamp No. 1 will be flashed three times in succession during each of the periods, and. so on, the table shown in Fig. 12 indicating the lamps which are flashed during each of the three spaced signaling periods for each of the possible operative positions 0-23 and 0-23 of switches fiFB and BFA respectively.

It will be seen that just prior to the commencement of each signaling cycle, i. e. when switch BSS is occupying position 24, an audible alarm is given on the bells such as 92 over lead 91.

This code call signaling operation will be proceeding while the finder switch fiUF, Fig. 9, is finding the calling line and it continues until the wanted subscriber answers the signal by dialinga common answering code number from any convenient telephone.

When this is done, the H relay in the local link taken into use by this party switches in over the P contact of the answering code number in the connector switch bank FSM to relay 6P, Fig. 10, whereupon the battery via common lead 90 and resistor GYB applied to the incoming negative.

lead at this point trips the ringing from the local AQMQQ link; and so. brings up the F-relay: therein, which relay connects. relay D to the incoming negative.

and positive conductors. Relay 6? in operating, at. contacts 5P! locks independently of relay 61 1B, at contacts SP2 and SP3. disconnects relay on from across the negative and positive lines er:- tending to the original calling party, at contacts 6P4 maintains a holding circuit for relay 6K independently of contacts 63?.132, and at contacts 6P5, Fig. 11 maintains the busy tone circuit to lead CCB independently of contacts erase. On the release of relay 6A, relay BKB releases, whereupon at contacts EH33 the negative and positive leads incoming via the multiple ESM from the wanted subscriber are connected through to the original calling subscriber. At contacts fiKBl the. operating circuit for relay ESC is opened so that when switch ESS next reaches the home position relay 650 will fail to hold and in. releasing will, prevent a further code signaling cycle from recommencing.

The two parties now converse via the code call link. and the local link taken into use by the want? ed party, the original calling party now acting as the called party and being supplied b battery feeding current Via rela D in the local link.

During conversation one or more other local links can switch in via their CR relays to the code call link relay 6ST but so long as relay eP remains, operated no further driving circuits be completed for the code finder switches. The calllug subscribers. concerned will receive busy tone via lead CCB and their respective local links, and theywill hold on until the code call link becomes available.

At. the end of the conversation, when the par tieshang up, the local link taken into use is released in usual manner, and relay 6P is also released. Relay GP in releasing brings down relay 6K and disconnects the CCB lead busy tone circuit. At the same time. it completes homing circuits for the code finder switches and when these switches reach home a circuit is completed to re-operate relay ESE, whereupon the code finder switches will search for and switch through to the first one of the wanted lines which is encountered, after which the operations follow in the manner already described. Any other waiting local links will again receive busy tone until such time as they can be dealt with in turn.

As mentioned previously, it. is not essential for the code call link to associate itself by finding with the calling party and then to release the original local link, since this link could be re tained in the connection between the calling party and the code call link. In this instance the calling line finder equipment of Fig. 9 would not be required and relay BKR, Fig. 10 would be permanently connected to parallel connected contacts EKKI and EKRZ by the connection shown in Fig. 9 comprising lines intercepted by circles. In this event when the wanted party dialed the common answering code number, the subsequent conversation would be effected via the link taken into use by the calling wanted party, the switches GPA and BFB of the code call link and the original local link taken into use by the original calling party.

In case a code call link on being started up is unable to find the wanted line, the code finder switch FA will rotate through to position 24 where relay BKK will operate in series with relay BLC to stop the finding operation. Relay tLC at contacts BLCI disconnects the series holding circuit between relay EST and relay CR in the calling local link. Relay GKK inoperating disconnects the; finder switch magnet driving circuit but in this instance is unable. to operate relay GKR since no. earth supply is available. from the P lead. in the connector switch multiple FSM so that the code call link finder is not set into operation. Relay OR in the local link in releasing opens the operating; circuit for relay BSR. via the CCM lead,. while relay 6ST in releasing opens the circuit of the other winding of relay GSR which thereupon releases and at contacts 68R? opens the circuit, of relay GKK. Relay GKK in releasing completes a homing; circuit for the. one or both of the, code finder switches which. have been brought into op-- eration. The code call link is thus freed for further use, while if the ringing has not been tripped in the local link the calling subscriber will C011? tinue. to receive ringing tone and the called subscriber will continue to be rung.

It, will be understood, that the P. A. X. board is not limited in scope to 100 lines capacity since by providing connecting switches of the 200-point type and by operating the link finder switches in two separate and distinct 100-line groups, a board of an ultimate capacity" of 200 lines can be readily provided.

It should also be mentioned that the invention may find application to private automatic branch exchanges and to rural exchanges either of automatic or semi-automatic. type.

I claim:

1. In a telephone: system, subscribers" stations having individual call signals, code call control equipment, code call signals wired in a common circuit to said control equipment. for code signaling the subscribers of said stations independent of said individual call signals, an individual code being, assigned to each, of said subscribers desired to be signaled by means of said code call signals, means operated by a calling station for completing a connection with a called station to cause the actuation of the individual call signal of said called station, said called station remaining unanswered, means in said connection thereafter responsive to the performance of an additional operation by said calling station for causing said control equipment to; actuate said code call signals in accordance with. the code assigned to the subscriber of said called station, and means res sponsive to the. code signaled subscriber answering said code call signaling by dialing a common code call, answering number at one of said stations for causing the discontinuance of said code call signaling and for connecting said calling and said on S ations together.

2. Ifhe structure defined in, claim 1 in which the, distinctive operation performed at the calling station is, the; same regardless of the code call signaling. code of the wanted subscriber.

3. In a telephone system, subscribers stations each having a call signal and a dial, a code call control unit, code call signals connected to said control unit for signaling subscriber-s individually by means of different code signal interruptions, means responsive to the operation of said dial at a calling station for completing a connection with a called station thereby to cause the actuation of said called stations individual call signal, said called station remaining unanswered,

means in said connection responsive to the diala common code call answering number at one of said stations for causing the disablement of said code call signaling and for establishing a talking connection between said calling station and said one station.

4. In a telephone system, a calling station having a dial, 9, called station having a call signal, multiple call signals, a control unit for actuating said multiple call signals in accordance with a particular code assigned for signaling the subscriber of said called station over said multiple cal]v signals, means responsive to the operation of said dial at said calling station'for completing a connection to said called station thereby to cause the actuation of said call signal of said called v station, said called station remaining unanswered, a condenser, a relay, means in said connection responsive to the dialing of an additional digit of predetermined value at said calling station for charging said condenser, means for dis- 4 charging said condenser thereby to operate said relay, said operation of said relay causing said control unit to actuate said multiple call signals in accordance with said particular code.

5. In a telephone system, subscribers stations each having a call signal and a dial, code call signals, a control unit for actuating said code call signals in accordance with different codes assigned to the subscribers of different stations,

means responsive to dialing at a calling station for completing a connection with a called station thereby to cause the actuation of the individual call signal of said called station, said called station remaining unanswered, a condenser, means in said connection responsive to said calling station dialing an additional digit of predetermined value for charging said condenser, means for discharging said condenser thereby to cause said control unit to actuate said code call signals in accordance with the code assigned to the subscriber of said called station, and means responsive to the code signaled subscriber dialing a code call answering number at one of said stations for causing the discontinuance of said code call signaling and for connecting said calling and said one stations together.

6. In a telephone system, subscribers stations each having a call signal and a dial, code call signals, a control unit for operating said code call signals in accordance with different codes assigned to the subscribers of different ones of said stations, means responsive to dialing at a calling station for completing a connection from said calling station to a called station and for causing the actuation of the individual call signal of said called station, a subscriber answering at said called station in response to said actuation of said individual call signal and informing said calling station that the desired subscriber of said called station cannot b reached at said called station, said answering subscriber thereafter retiring from said connection, a condenser, means in said connection responsive to said calling station dialing an additional digit of predetermined value for charging said condenser, means for discharging said condenser thereby to cause said control unit to operate said code call signals in accordance with the code of the desired subscriber, and means responsive to the code signaled subscriber dialing a common code call answering number at one of said stations for causing said calling and said one stations to be connected together and for causing said control unit to discontinue operating said code call signals.

7. In a telephone system, subscribers stations each having a signal, a common control unit having means for selecting different ones of said stations, multiple signals for signaling the subscribers of different stations by means of different codes, links, means for causing a link to connect with a calling station, means in said link controlled by said calling station for causing the operation of the individual signal of a called station, said called station remaining unanswered, means in said link responsive to the performance of another operation at said calling station for causing said unit to actuate said multiple signals in accordance with the code of the subscriber of said called station, said last means also causing said selecting means of said unit to connect with said calling station, means responsive to said connection of said selecting means for releasing said link, means controlled by the code-signaled subscriber at a third station for causing another link to connect with said third station, means in said other link controlled by said code-signaled subscriber for connecting said third station to said unit, and means responsive to said last connecting of said third station for causing said unit to discontinue actuating said multiple signals and to connect said third station with said calling station.

OWEN AVIS PEARCE.

REFERENCES CITED The following references are of record in the file of this pat-ent:

UNITED STATES PATENTS Number Name Date 1,504,215 Clausen Aug. 12, 1924 1,594,610 Gardner Aug. 3, 1926 2,324,341 Waller July 13, 1943 FOREIGN PATENTS 1 Number Country Date 498,520 Great Britain Jan. 9, 1939 

